Wireless communication systems are widely deployed to provide, for example, a broad range of voice and data-related services. Typical wireless communication systems consist of multiple-access communication networks that allow users of wireless devices to share common network resources. These networks typically require multiple-band antennas for transmitting and receiving radio frequency (“RF”) signals from wireless devices to infrastructure equipment such as a base station. Examples of such networks are the global system for mobile communication (“GSM”), which operates between 890 MHz and 960 MHz; the digital communications system (“DCS”), which operates between 1,710 MHz and 1,880 MHz; the personal communication system (“PCS”), which operates between 1,850 MHz and 1,990 MHz; and the universal mobile telecommunications system (“UMTS”), which operates between 1,920 MHz and 2,170 MHz.
Emerging and future wireless communication systems may require wireless devices and infrastructure equipment to operate new modes of communication at different frequency bands to support, for instance, higher data rates, increased functionality and more users. Examples of these emerging systems are the single carrier frequency division multiple access (“SC-FDMA”) system, the orthogonal frequency division multiple access (“OFDMA”) system, and other like systems. An OFDMA system is supported by various technology standards such as evolved universal terrestrial radio access (“E-UTRA”), Wi-Fi, worldwide interoperability for microwave access (“WiMAX”), wireless broadband (“WiBro”), ultra mobile broadband (“UMB”), long-term evolution (“LTE”), and other similar standards.
Moreover, wireless devices and infrastructure equipment may provide additional functionality that requires using other wireless communication systems that operate at different frequency bands. Examples of these other systems are the wireless local area network (“WLAN”) system, the IEEE 802.11b system and the Bluetooth system, which operate between 2,400 MHz and 2,484 MHz; the WLAN system, the IEEE 802.11a system and the HiperLAN system, which operate between 5,150 MHz and 5,350 MHz; the global positioning system (“GPS”), which operates at 1,575 MHz; and other like systems.
Many wireless communication systems in both government and industry require a broadband, low profile antenna. Such systems may require antennas that simultaneously support multiple frequency bands. Further, such systems may require dual polarization to support polarization diversity, polarization frequency re-use, or other similar polarization operation.
In addition, smart antennas such as beamforming antennas can be used to increase capacity, reduce co-channel and adjacent channel interference, improve range, reduce transmitted power, and mitigate multipath propagation effects in wireless communication systems. Smart antennas can direct electromagnetic RF energy in a preferred direction such as towards the antenna of a base station. A smart antenna is typically composed of multiple radiating elements that can be switched into certain configurations to shape and direct an antenna-pattern beam.
However, smart antennas can suffer from a number of limitations including performance degradation from environmental-related conditions. Such conditions can include the presence of a user or an object near the smart antenna; multipath propagation effects; the speed of the wireless device traveling through a network; and other similar effects. The impact of such environmental conditions can result in, for instance, dropped calls, increased transmit power levels, lower data rates, higher power consumption, and other similar effects. As such, it is desirable to have a smart antenna that can adapt to such environmental conditions.
Skilled artisans will appreciate that elements in the accompanying figures are illustrated for clarity, simplicity and to further help improve understanding of the exemplary embodiments, and have not necessarily been drawn to scale.